Space heater



`Iuly 23, 1957 T. 1. cosTELLo :TAL

v SPACE HEATER Y Filed Jan. 15, 1954 .l www... :ww LI m p .s WM Q.- WM L, w, n IIIIL QN. HHHHu ||l||||1 ,v/ www .MW l Wm w SPACE HEATER Timothy J. Costello and George T. Costello, St. Paul, Minn., assignors to National Heater Company, Inc., St. Paul, Minn., a corporation of Minnesota Application January 13, 1954, Serial No. 403,719

2 Claims. (Cl. 126-110) This invention relates to space heaters and hot air furnaces and more particularly, to high capacity heaters which are adapted to provide maximum heat production for large areas at a low operating cost, yet being of pleasing appearance and occupying but a relatively small oor area. Our improved heater is particularly adapted for industrial, commercial, educational and public buildings.

It is an important object of the invention to provide a compact space heater or hot air furnace unit having a high efficiency of heat exchange and adapted to rapidly circulate and recirculate the entire air content of a building by forced means.

It is a further object of the invention to provide in a hot air furnace or circulating heater, a highly eiiicient combinative relationship of a combustion chamber, constituting a primary heat exchanger, with closely overlying tubular members constituting a secondary heat exchanger, and blower units for efficiently picking up heat from the exchangers to extract a high ratio of heat for the size of the unit.

A further object of the invention is to provide a device of the class described in which the particular configuration and arrangement of the combustion chamber or lire box and the secondary heat exchanging tubes is such with respect to the blower elements as will permit a high rate of combustion within the combustion chamber while preventing overheated local areas which would shorten the effective life of the furnace.

It is another object of the invention to provide a high capacity and trouble-free space heater of the class described wherein all the heat exchanging elements, including the combustion chamber, may be efficiently constructed from plate or sheet metal material of comparatively light construction as contrasted with cast metal or refractory construction.

It is a still further object of the invention to provide for a heat exchanger which will employ transverse, generally concurrent heat exchange rather than counterflow, yet which will veffect a high degree of heat recovery while preserving unrestricted lues and preventing condensation of soot and tarry combustion products within the flues comprising the secondary heat exchanger.

These and other objects and advantages of our invention will more fully appear from the following description made in connection with the accompanying drawings wherein like reference characters refer to similar parts throughout the several views and in which:

Fig. l is a front elevation of our space heater showing the relationship between the primary and secondary heat exchangers, a portion of the housing being cut away to better show the internal structure of the parts and the burner being removed from the front of the housing to better show the mounting structure thereof. Hidden portions of the heater are indicated in dotted lines; and

Fig. 2 is a vertical section of the space heater taken on the line 2-2 of Fig. 1, portions of the structure being broken away and others shown in full line.

Referring more particularly to the drawing, 'our 'space nited States Patent i 2,800,126 Patented July 23, 1957 ICC heater has a housing construction indicated generally at 10, the housing comprising a blower chamber 11, a primary heat exchanging chamber 12, a secondary heating chamber 13 and hot air discharge passageways 14. The housing 10 is preferably of rectilinear construction and has framing members indicated generally at 1S and comprising a plurality of upright members 16, as well as horizontal members 17 and interconnecting braces 18. The housing has an atmospheric air intake through the sides of the blower chamber such as through louvers 19 and is provided with hot air discharge members 20 communicating with the discharge outlets 14 at the top of the housing. Other openings and connections with the Various parts of framework 15 will be pointed out as this specication progresses.

Our invention includes a primary heat exchanger in the form of the combustion chamber or fire box which is indicated generally at 21 and comprises an elongated member which is mounted horizontally within the housing 10 and is constructed of relatively thin metal plate having a high degree of resistance to heat. We prefer to use metal alloy having a steel base and a relatively high percentage of nickel and chromium although we do not wish to be restricted to any particular type of heat resisting metal. The combustion chamber 21 has a cross section in the outline of a teardrop terminating upwardly in an apex 22 as shown. It is preferred that the configuration be maintained uniformly from one end of the combustion chamber to the other so as to prevent pocketing of hot gases within the chamber which may cause local areas thereof to overheat and become damaged. Through considerable experimentation, we have found that the particular configuration disclosed herein is extremely elcient, both with respect to the travel of com bustion gases longitudinally and internally of the tube, as well as with respect to atmospheric air which has passed in contact with the external portions thereof, details of which will be described under the operation of the heat exchanger. The forward end of the combustion chamber 21 is provided with a front plate 23 which in turn supports anannular refractory member 24 having med-ially an opening 2S through which the hot burning gases are introduced. The annular refractory member 24 is encased by a reduced cylindrical extension 26 of the forward end of fire box orcombustion chamber 21 and this cylindrical portion is provided with an annular ring 27 which lies in slight spaced clearance with the front plate 28 of housing 10. A larger annular plate 29 is mounted in slight spaced clearance with the housing front 28 and is secured to the annular flange 27 by such means as stud rods or bolts 30 which are welded to the liange 27 and extend through drilled openings 31` formed through vthe housing front 2S. The studs 30 may be threaded at their outer ends so as to threadedly receive nuts 32 for rigidly supporting the plate 29 with relation to the combustion chamber 21 and its cylindrical extension 26.

The burner 33 is mounted to the plate 29 at the forward end of and in rigid relation with the combustion chamber 21 and having the proper packed relationship with the opening 25 so as not to admit air during the operation of the burner 33. The burner 33 may be of any conventional type, including gas burners, oil burners or combination oil and gas burners. The particular burner 33 is of the oil burner type, having a motor 34, a burner blower 35, and a supply line 36 for bringing liquid fued oil to the burner for atomization and mixture with air during combustion.

The 'combustion chamber 21 and the burner 33 are supported rigidly with respect to the rear end plate 37 of filed January 13, 1954, executed of even date herewith. The rigid connection is attained through combustion gas header 38 which is in communication with the discharge end of the combustion chamber 21, the teardrop configuration beingwelded thereto in fiuid tight union. The lower end of the header 3S is supported on cross member 39 which in turn is rigidly connected to the horizontal members 17 of the framework 15. An access doorway 40 is provided in the header 38 so as to be in alignment with combustion chamber 21. The access doorway 40 extends through the rearwall 37 of housing 10 and may be provided with a door d1 having a peep sight 42 for observing the character of the flame within fire box 21 during operation of burner 33. The header 3S may be provided with other access doorways 43 and 44 which also extend through the rear 37 of housing 10 and are provided with doors 45 and 4,6 respectively which may be normally retained in covering relation by such means as fastening bolts 47.

`Flanged connections 43 may provide additional connecting support and for maintaining in air tight relation between the access doorways and the housing 10.

Communicating with the discharge end of the primary heat exchanger' 21 and extending longitudinally over the primary heat exchanger, is a secondary heat exchanger indicated generally at 49 and preferably comprising a plurality or bank of metal tubular members 50 each in communication at its rear end with an upper extension 51 of the header 38, said upper extension projecting laterally from the upper downwardly outwardly sloping side portions of the combustion chamber 21. The tubes 50 are preferably arranged so as to completely fill the space between the upper part of the combustion chamber 21 including the upper downwardly outwardly sloping side portions thereof and the housing as shown in Figs. 1 and 2, being in staggered spaced clearance, one with the other, and at least a portion of the tubular members 50 lying in overlying air channeling relation with the upper teardrop surface of combustion chamber 21. The spacing between the tubes is preferably greater toward the top to prevent undue restriction at the discharge. The tubular members 50 terminate in communication with the outlet header 52 which in turn overlies the forward end of combustion chamber 21 in a generally inverted V-shape as shown in Fig. 1, the lower ends or legs 53 being firmly supported on the upright members 54 which in turn form a part of, or are rigidly secured, to the framework and to the sides of housing 10. The outlet header 52 has a reduced cylindrical pipe 55 which extends through the forward end 2S of housing 10 and communicates with the vent pipe 56 as shown in Fig. 2. Eye members 57 and 5S are secured to the headers 52 and 38 respectively for the purpose of forming means for suspending from crane hooks when the fire box assembly is lowered into the housing 1l? during the construction and assembly thereof. The suspension assembly for the burner and front end of the combustion chamber comprises a first member such as the U-shaped rod 59 which is welded to the header 52 as shown in Fig. 2 and a second suspension member 60 which has a rearwardly extending end 61 secured to the top of the teardrop configuration of combustion chamber 21 and extends in supported relation through the U-bar 59 in a forwardly extending loop 62 and then reversely bent to a depending end 63 which is secured as by welding to the front plate 23 of the combustion chamber 21. The blower housing 11 is provided with blower means suchvas a plurality of centrifugal blowers 64, all being driven by a common shaft 65 which is journaled in spaced bearings 66 mounted on cross brace members 18 as shown. A motor 67 having a drive sheave 68 rotates the shaft 65 through means of belt 69 and driven sheave 70. The centrifugal blowers 64 are provided with blades 71 rotatably secured to the shaft 65 and mounted within blower housing 72 as shown in Figs. 1 and 2. Each blower hous- `ing`72'has an expanded outlet 73 which extends across the housing space and divides the blower chamber 11 from the heat exchanger chamber 12. The expanded openings 73 underlie the teardrop configuration on combustion chambers 21 along the length of the housing for introducing air upwardly in streamlined ow against the teardrop configuration.

In the operation of our space heater the burner 33 and the blower motor 67 are energized in conventional manner and hot combustion gases are introduced into the head end of the combustion chamber 21. The hot gases fiow smoothly through the teardrop configuration, as well as through the remainder of the combustion chamber. The hot combustion gases then enter the header 38 and are reversely directed into the plurality of tubes 50 from which they are again collected in the outlet header 52 and are discharged into the chimney pipe 56.

The cool atmospheric air is drawn into the blower memcrs 64 in conventional manner and are discharged beneath the combustion chamber 21 uniformly along the length thereof. The cool atmospheric air is caused to pick up heat from the combustion chamber 21 and to flow smoothly along the sides thereof and up to the top of the apexed teardrop. Where the combustion chamber 21 has a cross sectional configuration such as a circle or a polygon, air turbulence will be set up at the external surface of the chamber and hot local areas will be created in the vicinity of the eddy currents. The preheated air leaving the outside of the combustion chamber 21 is then passed between the tubular members 5i) and at this point air turbulence is encouraged rather than discouraged. The air continues upwardly and picks up additional heat from the secondary heat exchanging tubes 50 and then passes outwardly through the passageway 14 and outlet members 20. Because of the incoming atmospheric air being preheated by flrst Contact with the combustion chamber 21, the air will not chill the secondary tubes 50 to a degree where air, soot and products of combustion will condense and collect on the inside surface of the tubes. Because of the efficiency of our simple design, we have found no additional benefits are to be gained by providing fins or bafiies. We have thus obviated the necessity for such expensive expedients.

It may thus be seen that we have devised a compact and efficient space heater in which a high volume of heat can be transferred to atmospheric air without danger of burning out the combustion chamber and without necessitating frequent cleaning of the secondary heating tubes.

lt will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of our invention as defined in the following claims.

What we claim is: Y

l. In a space heater or the like, an elongated horizontally disposed combustion chamber of uniform cross sectional area throughout constructed solely of relatively thin metal plate of high heat resistance, the upper part of said combustion chamber having a medial elongated area with substantially plane wall portions sloping upwardly and inwardly at each side along the length thereof and meeting substantially at their upper ends, the lower part of the combustion chamber having a medial elongated area with oppositely disposed meeting wall portions along the length thereof extending transversely at a downward and inward inclination, a housing enclosing said combustion chamber and having clearance therewith to define air passageways between the same and the sides of the combustion chamber, said housing being of general rectangular shape having vertical side walls and oppositely disposed longitudinally extending top wail portions substantially opposite the upper combustion chamber wall portions and sloping upwardly inwardly transversely from the upper ends of the vertical side walls at a similar inclination, a burner mounted at the forward end of the combustion chamber to direct dame into and to supply hot combustion gases thereto for longitudinal travel rearwardly throughout the ,length thereof and discharge at the rear end of the same,

a combustion gas header extending upwardly above and to both sides of and in communication with the rear end of the combustion chamber, a bank of tubular members extending longitudinally exteriorly of the combustion chamber in relatively close clearance with each other across the entire passageway at each side of and with the inner ones of the bank of tubular members in close overlying relation with said inwardly sloping upper side portions of the combustion chamber, said upper inwardly sloping top wall portions closely overlying outermost tubular members of said bank of tubular members, a combustion gas outlet header straddling the forward end portion of the combustion chamber extending upwardly above and to both sides of the forward end portion of the combustion chamber, said tubular members each communicating at its rear end with said first mentioned header and extending forwardly therefrom and communicating at its forward end with said combustion gas outlet header, said housing having a cool air inlet below said combustion chamber, and means for creating a forced circulation of atmospheric cool air upwardly against the underside of said combustion chamber and in balanced streamlined uniform contact therewith at the respective sloping sides thereof and in e turbulent uniform flow between said plurality of tubular members at each side of the combustion chamber for picking up additional heat therefrom before discharge from said housing, said means including an elongated cool air supply inlet means adjacent the underside of the combustion chamber, said cool air inlet means facing upwardly and extending substantially throughout the length of the combustion chamber, and having the longitudinal center thereof in vertical alignment with the medial line of the lower part of the combustion chamber, said housing being provided with a plurality of hot air discharge outlets along the top thereof, each of said hot air discharge outlets being located in vertical alignment with the medial line of the upper and lower parts of the combustion chamber and with the longitudinal center of said elongated air supply inlet means.

2. In a space heater or the like, an elongated horizontally disposed combustion chamber Iof uniform crosssectional area throughout constructed solely lof relatively thin metal plate of high heat resistance, the upper part of said combustion chamber having a medial elongated area with substantially plane wall portions sloping upwardly and inwardly at each side along the length thereof and meeting substantially at their ends, the lower part of the combustion chamber having a medial elongated area with oppositely disposed meeting side wall portions along the length thereof extending transversely at a downward and inward inclination, a housing enclosing said combustion chamber and having clearance therewith to define air passageways between the same and the sides of the combustion chamber, a burner mounted at the forward end of the combustion chamber to direct flame into and to supply hot combustion gases thereto for longitudinal travel rearwardly throughout the length thereof and discharge at the rear end of the same, a combustion gas header extending upwardly above and to both sides lof and in communication with the rear end of the combustion chamber, a bank of tubular members extending longitudinally exteriorly of Cil the combustion chamber in relatively close clearance with each other across the entire passageway at each side of and with the inner ones of the bank of tubular members in close overlying relation with the wall portions dening said upper part of the combustion chamber, the upper wall portions of said housing closely overlying outermost tubular members of said bank of tubular members and said tubes being densely packed above and on lopposite sides of the wall portions defining said upper part of the combustion chamber and so positioned relative to each other as to impede the flow of air in a generally vertical direction, the upper walls -of the housing, the shape of the wall portions defining said upper part of the combustion chamber and the disposition of said tubes with respect to each other and to the walls of the housing and said wall portions defining said upper part of the combustion chamber cooperating to present upwardly converging free paths of least flow resistance immediately adjacent to and on opposite sides of and in intimate contact with the opposite sides of the wall portions defining said upper part of the combustion chamber to confine the overall ow of the air such that said overall flow of air is crowded upwardly toward a region at the top of the housing and wherein the air flowing through said free paths is crowded toward a line in vertical alignment with the longitudinal medialline of the wall portions delning said upper part of the combustion chamber, a combustion gas outlet header straddling the forward end portion of the combustion chamber extending upwardly above and to both sides of the forward end portion of the combustion chamber, said tubular members each communicating at its rear end with said first mentioned header and extending forwardly therefrom and communicating at its forward end with said combustion gas outlet header, said housing having va cool air inlet below said combustion chamber, means for creating a forced circulation of cooled air upwardly through said air inlet opening and against said lower part ofthe combustion chamber, the longitudinal center line of said air inlet opening being substantially in vertical alignment with the medial line of said lower part of the combustion chamber whereby incoming air is substantially equally divided on both sides of said lower part of the combustion chamber to effect a continuous wiping action throughout the area of the same to avoid the occurrence of hot spots in the lower part of the combustion chamber, outlet means in the top of said housing for receiving said flow of air after it passes over said tubes and the wall portions defining said upper part of the combustion chamber.

References Cited in the tile of this patent UNITED STATES PATENTS 315,040 Jones Apr. 7, 1885 1,013,304 Noble Ian. 2, 1912 2,160,269 Iorolemon May 30, 1939 2,172,667 Nelson Sept. 12, 1939 2,376,140 Henderson May 15, 1945 FOREIGN PATENTS 572,106 Great Britain Sept. 14, 1945 

